Annapurna Base Camp is a Grade B or a moderately difficult trekking route. So any fit person can do this trek, even if you do not have any previous experience. You should be aware of what to expect and mentally prepare for it. Then, as long as you will too, you can.

The highest altitude reached is 4190m. This is the elevation of Annapurna Base Camp. ABC is the highest we will climb in this trek.

Yes, you can charge batteries en route. Charger should be brought. There are hot shower facilities as well. You may have to pay a certain amount for both ($1-$2). Negotiate. Also, a hot water facility could be free at a lower elevation.

Yes. The Internet can be accessed in most places. Sometimes, there might be some technical problems. The Internet in Nepal is not as fast as you are used to and at times you can just lose connection.